Computational Modeling and Simulation for Nanomaterials, Nanotechnology, and Nanoscience - II

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Theory and Simulation of Nanostructures".

Deadline for manuscript submissions: closed (31 March 2023) | Viewed by 41010

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Department of Architecture, University of “Roma Tre”, Rome, Italy
Interests: nonlinear dynamics and stability; carbon nanotube composites; multi-scale, computational mechanics and multiphysics; non-standard finite element formulation and implementation; advanced numerical solvers for nonlinear problems; meta-heuristic algorithms for optimization
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Special Issue Information

Dear Colleagues,

Following up on the successful outcome of the previous Special Issue on “Computational Modeling and Simulation for Nanomaterials, Nanotechnology, and Nanoscience”, we aim to attract and report the rich variety of recent research findings in the field of nanomaterials, nanostructures, and processes with a focus on combining experimental and theoretical efforts enabled by computational modeling and simulations. Our aim is to further develop all the enhanced solutions for investigating the surprising properties associated with various phenomena that occur at the nanoscale through models, simulations, and experiments. In the present Special Issue, we will emphasize contributions at the macro-scale level of nanomaterials and nanosystems that would provide a significant advancement of knowledge in the large array of technological applications, ranging from biomedical to industrial engineering.

Prof. Dr. Giovanni Formica
Guest Editor

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Keywords

  • physical nanomaterial models for experimental design and characterization
  • mesoscopic/macroscopic formulations
  • multi-scale computational approaches
  • coupled, multi-physics problems
  • carbon nanotube nanocomposites

Published Papers (26 papers)

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Research

12 pages, 4300 KiB  
Article
Tunable Magnetic Properties of Interconnected Permalloy Nanowire Networks
by Alejandro Pereira, Guidobeth Sáez, Eduardo Saavedra and Juan Escrig
Nanomaterials 2023, 13(13), 1971; https://doi.org/10.3390/nano13131971 - 29 Jun 2023
Cited by 1 | Viewed by 1238
Abstract
In this study, we investigate the magnetic properties of interconnected permalloy nanowire networks using micromagnetic simulations. The effects of interconnectivity on the hysteresis curves, coercivity, and remanence of the nanowire networks are analyzed. Our results reveal intriguing characteristics of the hysteresis curves, including [...] Read more.
In this study, we investigate the magnetic properties of interconnected permalloy nanowire networks using micromagnetic simulations. The effects of interconnectivity on the hysteresis curves, coercivity, and remanence of the nanowire networks are analyzed. Our results reveal intriguing characteristics of the hysteresis curves, including nonmonotonic behaviors of coercivity as a function of the position of horizontal nanowires relative to vertical nanowires. By introducing horizontal nanowires at specific positions, the coercivity of the nanowire networks can be enhanced without altering the material composition. The normalized remanence remains relatively constant regardless of the position of the horizontal wires, although it is lower in the interconnected nanowire arrays compared to nonconnected arrays. These findings provide valuable insights into the design and optimization of nanowire networks for applications requiring tailored magnetic properties. Full article
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19 pages, 4685 KiB  
Article
Nonlinear Dynamic Response of Nanocomposite Microbeams Array for Multiple Mass Sensing
by Giovanni Formica, Walter Lacarbonara and Hiroshi Yabuno
Nanomaterials 2023, 13(11), 1808; https://doi.org/10.3390/nano13111808 - 05 Jun 2023
Cited by 3 | Viewed by 988
Abstract
A nonlinear MEMS multimass sensor is numerically investigated, designed as a single input-single output (SISO) system consisting of an array of nonlinear microcantilevers clamped to a shuttle mass which, in turn, is constrained by a linear spring and a dashpot. The microcantilevers are [...] Read more.
A nonlinear MEMS multimass sensor is numerically investigated, designed as a single input-single output (SISO) system consisting of an array of nonlinear microcantilevers clamped to a shuttle mass which, in turn, is constrained by a linear spring and a dashpot. The microcantilevers are made of a nanostructured material, a polymeric hosting matrix reinforced by aligned carbon nanotubes (CNT). The linear as well as the nonlinear detection capabilities of the device are explored by computing the shifts of the frequency response peaks caused by the mass deposition onto one or more microcantilever tips. The frequency response curves of the device are obtained by a pathfollowing algorithm applied to the reduced-order model of the system. The microcantilevers are described by a nonlinear Euler-Bernoulli inextensible beam theory, which is enriched by a meso-scale constitutive law of the nanocomposite. In particular, the microcantilever constitutive law depends on the CNT volume fraction suitably used for each cantilever to tune the frequency bandwidth of the whole device. Through an extensive numerical campaign, the mass sensor sensitivity estimated in the linear and nonlinear dynamic range shows that, for relatively large displacements, the accuracy of the added mass detectability can be improved due to the larger nonlinear frequency shifts at resonance (up to 12%). Full article
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13 pages, 7948 KiB  
Article
High-Throughput Computational Screening of Two-Dimensional Covalent Organic Frameworks (2D COFs) for Capturing Radon in Moist Air
by Hongyan Zeng, Xiaomin Geng, Shitong Zhang, Bo Zhou, Shengtang Liu and Zaixing Yang
Nanomaterials 2023, 13(9), 1532; https://doi.org/10.3390/nano13091532 - 03 May 2023
Viewed by 1500
Abstract
Radon (Rn) and its decay products are the primary sources of natural ionizing radiation exposure for the public, posing significant health risks, including being a leading cause of lung cancer. Porous material-based adsorbents offer a feasible and efficient solution for controlling Rn concentrations [...] Read more.
Radon (Rn) and its decay products are the primary sources of natural ionizing radiation exposure for the public, posing significant health risks, including being a leading cause of lung cancer. Porous material-based adsorbents offer a feasible and efficient solution for controlling Rn concentrations in various scenes to achieve safe levels. However, due to competitive adsorption between Rn and water, finding candidates with a higher affinity and capacity for capturing Rn in humid air remains a significant challenge. Here, we conducted high-throughput computational screening of 8641 two-dimensional covalent organic frameworks (2D COFs) in moist air using grand canonical Monte Carlo simulations. We identified the top five candidates and revealed the structure–performance relationship. Our findings suggest that a well-defined cavity with an approximate spherical inner space, with a diameter matching that of Rn, is the structural basis for a proper Rn capturing site. This is because the excellent steric match between the cavity and Rn maximizes their van der Waals dispersion interactions. Additionally, the significant polarization electrostatic potential surface of the cavity can regulate the adsorption energy of water and ultimately impact Rn selectivity. Our study offers a potential route for Rn management using 2D COFs in moist air and provides a scientific basis for further experimentation. Full article
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17 pages, 12098 KiB  
Article
Impacts of Random Atomic Defects on Critical Buckling Stress of Graphene under Different Boundary Conditions
by Jiajia Shi, Liu Chu, Zhengyu Yu and Eduardo Souza de Cursi
Nanomaterials 2023, 13(9), 1499; https://doi.org/10.3390/nano13091499 - 27 Apr 2023
Viewed by 792
Abstract
Buckled graphene has potential applications in energy harvest, storage, conversion, and hydrogen storage. The investigation and quantification analysis of the random porosity in buckled graphene not only contributes to the performance reliability evaluation, but it also provides important references for artificial functionalization. This [...] Read more.
Buckled graphene has potential applications in energy harvest, storage, conversion, and hydrogen storage. The investigation and quantification analysis of the random porosity in buckled graphene not only contributes to the performance reliability evaluation, but it also provides important references for artificial functionalization. This paper proposes a stochastic finite element model to quantify the randomly distributed porosities in pristine graphene. The Monte Carlo stochastic sampling process is combined with finite element computation to simulate the mechanical property of buckled graphene. Different boundary conditions are considered, and the corresponding results are compared. The impacts of random porosities on the buckling patterns are recorded and analyzed. Based on the large sampling space provided by the stochastic finite element model, the discrepancies caused by the number of random porosities are discussed. The possibility of strengthening effects in critical buckling stress is tracked in the large sampling space. The distinguishable interval ranges of probability density distribution for the relative variation of the critical buckling stress prove the promising potential of artificial control by the atomic vacancy amounts. In addition, the approximated Gaussian density distribution of critical buckling stress demonstrates the stochastic sampling efficiency by the Monte Carlo method and the artificial controllability of porous graphene. The results of this work provide new ideas for understanding the random porosities in buckled graphene and provide a basis for artificial functionalization through porosity controlling. Full article
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16 pages, 2332 KiB  
Article
Free Vibration Analysis of Functionally Graded Porous Cylindrical Panels Reinforced with Graphene Platelets
by Jin-Rae Cho
Nanomaterials 2023, 13(9), 1441; https://doi.org/10.3390/nano13091441 - 22 Apr 2023
Cited by 10 | Viewed by 1494
Abstract
The free vibration of functionally graded porous cylindrical shell panels reinforced with graphene platelets (GPLs) was numerically investigated. The free vibration problem was formulated using the first-order shear deformation shell theory in the framework of the 2-D natural element method (NEM). The effective [...] Read more.
The free vibration of functionally graded porous cylindrical shell panels reinforced with graphene platelets (GPLs) was numerically investigated. The free vibration problem was formulated using the first-order shear deformation shell theory in the framework of the 2-D natural element method (NEM). The effective material properties of the GPL-reinforced shell panel were evaluated by employing the Halpin–Tsai model and the rule of mixtures and were modified by considering the porosity distribution. The cylindrical shell surface was transformed into the 2-D planar NEM grid to avoid complex computation, and the concept of the MITC3+shell element was employed to suppress shear locking. The numerical method was validated through benchmark experiments, and the free vibration characteristics of FG-GPLRC porous cylindrical shell panels were investigated. The numerical results are presented for four GPL distribution patterns (FG-U, FG-X, FG-O, and FG-Λ) and three porosity distributions (center- and outer-biased and uniform). The effects of GPL weight, porosity amount, length–thickness and length–radius ratios, and the aspect ratio of the shell panel and boundary condition on the free vibration characteristics are discussed in detail. It is found from the numerical results that the proposed numerical method accurately predicts the natural frequencies of FG-GPLRC porous cylindrical shell panels. Moreover, the free vibration of FG-GPLRC porous cylindrical shell panels is significantly influenced by the distribution pattern as well as the amount of GPLs and the porosity. Full article
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13 pages, 2757 KiB  
Article
Characterization of Carbon-Black-Based Nanocomposite Mixtures of Varying Dispersion for Improving Stochastic Model Fidelity
by Tyler Albright and Jared Hobeck
Nanomaterials 2023, 13(5), 916; https://doi.org/10.3390/nano13050916 - 01 Mar 2023
Cited by 4 | Viewed by 1406
Abstract
Carbon black nanocomposites are complex systems that show potential for engineering applications. Understanding the influence of preparation methods on the engineering properties of these materials is critical for widespread deployment. In this study, the fidelity of a stochastic fractal aggregate placement algorithm is [...] Read more.
Carbon black nanocomposites are complex systems that show potential for engineering applications. Understanding the influence of preparation methods on the engineering properties of these materials is critical for widespread deployment. In this study, the fidelity of a stochastic fractal aggregate placement algorithm is explored. A high-speed spin-coater is deployed for the creation of nanocomposite thin films of varying dispersion characteristics, which are imaged via light microscopy. Statistical analysis is performed and compared to 2D image statistics of stochastically generated RVEs with comparable volumetric properties. Correlations between simulation variables and image statistics are examined. Future and current works are discussed. Full article
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20 pages, 4841 KiB  
Article
FDTD Simulations for Rhodium and Platinum Nanoparticles for UV Plasmonics
by Andrey Yurevich Zyubin, Igor Igorevich Kon, Darya Alexeevna Poltorabatko and Ilia Gennadievich Samusev
Nanomaterials 2023, 13(5), 897; https://doi.org/10.3390/nano13050897 - 27 Feb 2023
Cited by 5 | Viewed by 2013
Abstract
The article describes the results of finite-difference time-domain (FDTD) mathematical modeling of electromagnetic fields distortion near the surfaces of two transition metals: rhodium (Rh) and platinum (Pt) on glass (SiO2) substrates. Results were compared with calculated optical properties of classical SERS [...] Read more.
The article describes the results of finite-difference time-domain (FDTD) mathematical modeling of electromagnetic fields distortion near the surfaces of two transition metals: rhodium (Rh) and platinum (Pt) on glass (SiO2) substrates. Results were compared with calculated optical properties of classical SERS generating metals (Au and Ag). We have performed FDTD-based theoretical calculations for UV SERS-active nanoparticles (NPs) and structures based on hemispheres of Rh and Pt and planar surfaces, consisting of single NPs with varied gaps between them. The results have been compared with gold stars, silver spheres and hexagons. The prospects of the theoretical approach for single NPs and planar surfaces modeling to evaluate optimal field amplification and light scattering parameters have been shown. The presented approach could be applied as a basis for performing the methods of controlled synthesis for LPSR tunable colloidal and planar metal-based biocompatible optical sensors for UV and deep-UV plasmonics. The difference between UV-plasmonic NPs and plasmonics in a visible range has been evaluated. Full article
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12 pages, 2237 KiB  
Article
Mirroring Skyrmions in Synthetic Antiferromagnets via Modular Design
by Panluo Deng, Fengjun Zhuo, Hang Li and Zhenxiang Cheng
Nanomaterials 2023, 13(5), 859; https://doi.org/10.3390/nano13050859 - 25 Feb 2023
Cited by 1 | Viewed by 1437
Abstract
Skyrmions are promising for the next generation of spintronic devices, which involves the production and transfer of skyrmions. The creation of skyrmions can be realized by a magnetic field, electric field, or electric current while the controllable transfer of skyrmions is hindered by [...] Read more.
Skyrmions are promising for the next generation of spintronic devices, which involves the production and transfer of skyrmions. The creation of skyrmions can be realized by a magnetic field, electric field, or electric current while the controllable transfer of skyrmions is hindered by the skyrmion Hall effect. Here, we propose utilizing the interlayer exchange coupling induced by the Ruderman–Kittel–Kasuya–Yoshida interactions to create skyrmions through hybrid ferromagnet/synthetic antiferromagnet structures. An initial skyrmion in ferromagnetic regions could create a mirroring skyrmion with an opposite topological charge in antiferromagnetic regions driven by the current. Furthermore, the created skyrmions could be transferred in synthetic antiferromagnets without deviations away from the main trajectories due to the suppression of the skyrmion Hall effect in comparison to the transfer of the skyrmion in ferromagnets. The interlayer exchange coupling can be tuned, and the mirrored skyrmions can be separated when they reach the desired locations. Using this approach, the antiferromagnetic coupled skyrmions can be repeatedly created in hybrid ferromagnet/synthetic antiferromagnet structures. Our work not only supplies a highly efficient approach to create isolated skyrmions and correct the errors in the process of skyrmion transport, but also paves the way to a vital information writing technique based on the motion of skyrmions for skyrmion-based data storage and logic devices. Full article
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15 pages, 3688 KiB  
Article
Numerical Investigation of GaN HEMT Terahertz Detection Model Considering Multiple Scattering Mechanisms
by Qingzhi Meng, Qijing Lin, Zelin Wang, Yangtao Wang, Weixuan Jing, Dan Xian, Na Zhao, Kun Yao, Fuzheng Zhang, Bian Tian and Zhuangde Jiang
Nanomaterials 2023, 13(4), 632; https://doi.org/10.3390/nano13040632 - 05 Feb 2023
Cited by 1 | Viewed by 1255
Abstract
GaN high-electron-mobility transistor (HEMT) terahertz (THz) detectors have been widely studied and applied in the past few decades. However, there are few reports about the influence of GaN/AlGaN heterostructure material properties on the detection model at present. In this paper, a response voltage [...] Read more.
GaN high-electron-mobility transistor (HEMT) terahertz (THz) detectors have been widely studied and applied in the past few decades. However, there are few reports about the influence of GaN/AlGaN heterostructure material properties on the detection model at present. In this paper, a response voltage model for a GaN HEMT THz detector that considers the carrier scattering in a GaN/AlGaN heterostructure is proposed. The phonon scattering, dislocation scattering, and interface roughness scattering mechanisms are taken into account in the classic THz response voltage model; furthermore, the influence of various material parameters on the response voltage is studied. In a low-temperature region, acoustic scattering plays an important role, and the response voltage drops with an increase in temperature. In a high temperature range, optical phonon scattering is the main scattering mechanism, and the detector operates in a non-resonant detection mode. With an increase in carrier surface density, the response voltage decreases and then increases due to piezoelectric scattering and optical phonon scattering. For dislocation and interface roughness scattering, the response voltage is inversely proportional to the dislocation density and root mean square roughness (RMS) but is positively related to lateral correlation length. Finally, a comparison between our model and the reported models shows that our proposed model is more accurate. Full article
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19 pages, 4511 KiB  
Article
Elastic Strain Relaxation of Phase Boundary of α′ Nanoscale Phase Mediated via the Point Defects Loop under Normal Strain
by Zhengwei Yan, Shujing Shi, Peng Sang, Kaiyue Li, Qingqing Qin and Yongsheng Li
Nanomaterials 2023, 13(3), 456; https://doi.org/10.3390/nano13030456 - 22 Jan 2023
Viewed by 1197
Abstract
Irradiation-induced point defects and applied stress affect the concentration distribution and morphology evolution of the nanophase in Fe–Cr based alloys; the aggregation of point defects and the nanoscale precipitates can intensify the hardness and embrittlement of the alloy. The influence of normal strain [...] Read more.
Irradiation-induced point defects and applied stress affect the concentration distribution and morphology evolution of the nanophase in Fe–Cr based alloys; the aggregation of point defects and the nanoscale precipitates can intensify the hardness and embrittlement of the alloy. The influence of normal strain on the coevolution of point defects and the Cr-enriched α′ nanophase are studied in Fe-35 at.% Cr alloy by utilizing the multi-phase-field simulation. The clustering of point defects and the splitting of nanoscale particles are clearly presented under normal strain. The defects loop formed at the α/α′ phase interface relaxes the coherent strain between the α/α′ phases, reducing the elongation of the Cr-enriched α′ phase under the normal strains. Furthermore, the point defects enhance the concentration clustering of the α′ phase, and this is more obvious under the compressive strain at high temperature. The larger normal strain can induce the splitting of an α′ nanoparticle with the nonequilibrium concentration in the early precipitation stage. The clustering and migration of point defects provide the diffusion channels of Cr atoms to accelerate the phase separation. The interaction of point defect with the solution atom clusters under normal strain provides an atomic scale view on the microstructure evolution under external stress. Full article
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12 pages, 1183 KiB  
Article
Classical Analog and Hybrid Metamaterials of Tunable Multiple-Band Electromagnetic Induced Transparency
by Zhi Zhang, Duorui Gao, Jinhai Si and Jiacheng Meng
Nanomaterials 2022, 12(24), 4405; https://doi.org/10.3390/nano12244405 - 09 Dec 2022
Cited by 1 | Viewed by 1060
Abstract
The electromagnetic induced transparency (EIT) effect originates from the destructive interference in an atomic system, which contributes to the transparency window in its response spectrum. The implementation of EIT requires highly demanding laboratory conditions, which greatly limits its acceptance and application. In this [...] Read more.
The electromagnetic induced transparency (EIT) effect originates from the destructive interference in an atomic system, which contributes to the transparency window in its response spectrum. The implementation of EIT requires highly demanding laboratory conditions, which greatly limits its acceptance and application. In this paper, an improved harmonic spring oscillation (HSO) model with four oscillators is proposed as a classical analog for the tunable triple-band EIT effect. A more general HSO model including more oscillators is also given, and the analyses of the power absorption in the HSO model conclude a formula, which is more innovative and useful for the study of the multiple-band EIT effect. To further inspect the analogizing ability of the HSO model, a hybrid unit cell containing an electric dipole and toroidal dipoles in the metamaterials is proposed. The highly comparable transmission spectra based on the HSO model and metamaterials indicate the validity of the classical analog in illustrating the formation process of the multiple-band EIT effect in metamaterials. Hence, the HSO model, as a classical analog, is a valid and powerful theoretical tool that can mimic the multiple-band EIT effect in metamaterials. Full article
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13 pages, 3748 KiB  
Article
The Influence of Carbides on Atomic-Scale Mechanical Properties of Carbon Steel: A Molecular Dynamics Study
by Liang Zhang, Longlong Yang, Kun Sun, Pujie Zhu and Keru Chen
Nanomaterials 2022, 12(23), 4179; https://doi.org/10.3390/nano12234179 - 24 Nov 2022
Cited by 2 | Viewed by 1073
Abstract
Pearlite is an important structure in carbon steel; however, the influence mechanism of carbides in pearlite on its mechanical properties and microstructure evolution has not yet been fully elucidated. In this work, a ferrite–carbide composite model with various carbide types was constructed to [...] Read more.
Pearlite is an important structure in carbon steel; however, the influence mechanism of carbides in pearlite on its mechanical properties and microstructure evolution has not yet been fully elucidated. In this work, a ferrite–carbide composite model with various carbide types was constructed to investigate the influence of carbide types via a uniaxial compression deformation using classical molecular dynamics simulations. It was found that the carbide type had little effect on the compressive elastic modulus, but a more obvious effect on the yield strain, yield stress, and flow stress. The maximum compressive elastic modulus was in the Fe2C model, with 300.32 GPa, while the minimum was found in the Fe4C model at 285.16 GPa; the error was 5.32%. There were significant differences in the yield stress, yield strain, and flow stress of the ferrite–carbide model according to the stress–strain curve. Secondly, the type of carbide used affected its elastic constant, especially the bulk modulus and Cauchy pressure. The maximum bulk modulus of the Fe4C model was 199.01 GPa, the minimum value of the Fe3C model was 146.03 GPa, and the difference was 52.98 GPa. The Cauchy pressure calculation results were consistent with the yield strain trend. Additionally, the effective elastic moduli of the composite system were used to verify the accuracy of the calculation results of this work. Thirdly, ferrite–carbide interfaces could act as a resource for dislocation emission. The initial stacking fault forms at ferrite–carbide interfaces and expands into ferrite. The dislocation type and segment in the ferrite–carbide model were significantly different due to the type of carbide used. Full article
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12 pages, 1023 KiB  
Article
Hydrogenated Boron Phosphide THz-Metamaterial-Based Biosensor for Diagnosing COVID-19: A DFT Coupled FEM Study
by Chunjian Tan, Shaogang Wang, Huiru Yang, Qianming Huang, Shizhen Li, Xu Liu, Huaiyu Ye and Guoqi Zhang
Nanomaterials 2022, 12(22), 4024; https://doi.org/10.3390/nano12224024 - 16 Nov 2022
Cited by 1 | Viewed by 1425
Abstract
Recent reports focus on the hydrogenation engineering of monolayer boron phosphide and simultaneously explore its promising applications in nanoelectronics. Coupling density functional theory and finite element method, we investigate the bowtie triangle ring microstructure composed of boron phosphide with hydrogenation based on structural [...] Read more.
Recent reports focus on the hydrogenation engineering of monolayer boron phosphide and simultaneously explore its promising applications in nanoelectronics. Coupling density functional theory and finite element method, we investigate the bowtie triangle ring microstructure composed of boron phosphide with hydrogenation based on structural and performance analysis. We determine the carrier mobility of hydrogenated boron phosphide, reveal the effect of structural and material parameters on resonance frequencies, and discuss the variation of the electric field at the two tips. The results suggest that the mobilities of electrons for hydrogenated BP monolayer in the armchair and zigzag directions are 0.51 and 94.4 cm2·V1·s1, whereas for holes, the values are 136.8 and 175.15 cm2·V1·s1. Meanwhile, the transmission spectra of the bowtie triangle ring microstructure can be controlled by adjusting the length of the bowtie triangle ring microstructure and carrier density of hydrogenated BP. With the increasing length, the transmission spectrum has a red-shift and the electric field at the tips of equilateral triangle rings is significantly weakened. Furthermore, the theoretical sensitivity of the BTR structure reaches 100 GHz/RIU, which is sufficient to determine healthy and COVID-19-infected individuals. Our findings may open up new avenues for promising applications in the rapid diagnosis of COVID-19. Full article
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14 pages, 3042 KiB  
Article
Optical and Thermal Behavior of Germanium Thin Films under Femtosecond Laser Irradiation
by Ahmed Abdelmalek, Lebogang Kotsedi, Zeyneb Bedrane, El-Hachemi Amara, Marco Girolami and Malik Maaza
Nanomaterials 2022, 12(21), 3786; https://doi.org/10.3390/nano12213786 - 27 Oct 2022
Cited by 4 | Viewed by 1543
Abstract
In this study, we theoretically investigate the response of a germanium thin film under femtosecond pulsed laser irradiation. Electron and lattice temperatures, as well as material-specific optical properties such as dielectric function and reflectivity, were calculated during the irradiation using an extended two-temperature [...] Read more.
In this study, we theoretically investigate the response of a germanium thin film under femtosecond pulsed laser irradiation. Electron and lattice temperatures, as well as material-specific optical properties such as dielectric function and reflectivity, were calculated during the irradiation using an extended two-temperature model coupled with the carrier density rate equation and the Drude model. Melting and ablation fluence thresholds were also predicted, resulting in 0.14 J cm−2 and 0.35 J cm−2, respectively. An ultrafast change in both optical and thermal properties was detected upon laser irradiation. Results also indicate that thermal melting occurs after germanium takes on a metallic character during irradiation, and that the impact ionization process may have a critical role in the laser-induced thermal effect. Therefore, we suggest that the origin of the thermal modification of germanium surface under femtosecond laser irradiation is mostly due the impact ionization process and that its effect becomes more important when increasing the laser fluence. Full article
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17 pages, 14313 KiB  
Article
Electro-Design of Bimetallic PdTe Electrocatalyst for Ethanol Oxidation: Combined Experimental Approach and Ab Initio Density Functional Theory (DFT)—Based Study
by Andile Mkhohlakali, Xolile Fuku, Min Ho Seo, Mmalewane Modibedi, Lindiwe Khotseng and Mkhulu Mathe
Nanomaterials 2022, 12(20), 3607; https://doi.org/10.3390/nano12203607 - 14 Oct 2022
Cited by 1 | Viewed by 1494
Abstract
An alternative electrosynthesis of PdTe, using the electrochemical atomic layer deposition (E-ALD) method, is reported. The cyclic voltammetry technique was used to analyze Au substrate in copper (Cu2+), and a tellurous (Te4+) solution was used to identify UPDs and [...] Read more.
An alternative electrosynthesis of PdTe, using the electrochemical atomic layer deposition (E-ALD) method, is reported. The cyclic voltammetry technique was used to analyze Au substrate in copper (Cu2+), and a tellurous (Te4+) solution was used to identify UPDs and set the E-ALD cycle program. Results obtained using atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques reveal the nanometer-sized flat morphology of the systems, indicating the epitaxial characteristics of Pd and PdTe nanofilms. The effect of the Pd:Te ratio on the crystalline structure, electronic properties, and magnetic properties was investigated using a combination of density functional theory (DFT) and X-ray diffraction techniques. Te-containing electrocatalysts showed improved peak current response and negative onset potential toward ethanol oxidation (5 mA; −0.49 V) than Pd (2.0 mA; −0.3 V). Moreover, DFT ab initio calculation results obtained when the effect of Te content on oxygen adsorption was studied revealed that the d-band center shifted relative to the Fermi level: −1.83 eV, −1.98 eV, and −2.14 eV for Pd, Pd3Te, and Pd3Te2, respectively. The results signify the weakening of the CO-like species and the improvement in the PdTe catalytic activity. Thus, the electronic and geometric effects are the descriptors of Pd3Te2 activity. The results suggest that Pd2Te2 is a potential candidate electrocatalyst that can be used for the fabrication of ethanol fuel cells. Full article
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17 pages, 3057 KiB  
Article
Analytical Model for Determination of Size-Distribution of Colloidal Silver Nanoparticles from Surface Plasmon Resonance Wavelength and Dielectric Functions
by Julio Car and Nikša Krstulović
Nanomaterials 2022, 12(19), 3474; https://doi.org/10.3390/nano12193474 - 04 Oct 2022
Viewed by 1645
Abstract
In this work it is shown that the size of silver nanoparticles in a colloidal solution can be determined only from the wavelength of the surface plasmon resonance and material and medium dielectric functions. The size dependence of dielectric functions of silver nanoparticles [...] Read more.
In this work it is shown that the size of silver nanoparticles in a colloidal solution can be determined only from the wavelength of the surface plasmon resonance and material and medium dielectric functions. The size dependence of dielectric functions of silver nanoparticles becomes noticeable in nanoparticles which are smaller than 30 nm in size, which is in accordance with Mie scattering theory applicability. The novelty of this work is in the development of an analytical model for the determination of the size of silver nanoparticles derived from applying shift functions to the UV-Vis spectra, resulting in well-known characteristic diameters of log-normal size distribution function. The purpose of these shift functions is the reconstruction of experimental UV–Vis spectra from simulated ones based on the Beer–Lambert law and log-normal distribution function in order to find the mode diameters of colloidal silver nanoparticles. The introduction of Lagrangian analogue of extinction cross section explains the redshift constant characteristic for given nanoparticle material and the size distribution of nanoparticles. Therefore, the size determination of colloidal silver nanoparticles is possible only through UV–Vis spectroscopy. Full article
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20 pages, 6040 KiB  
Article
Fitting Procedure to Reconstruct the Size Distribution and the Concentration of Silver Colloidal Nanoparticles from UV-Vis Spectra
by Julio Car and Nikša Krstulović
Nanomaterials 2022, 12(19), 3302; https://doi.org/10.3390/nano12193302 - 22 Sep 2022
Cited by 2 | Viewed by 1739
Abstract
In this work, a complete fitting procedure of UV-Vis spectra of silver nanoparticles in colloidal solutions is reported. The fitting function, based on the Beer–Lambert law, Mie theory, and log-normal probability distribution of nanoparticles’ sizes, is developed and confirmed by 33 different independent [...] Read more.
In this work, a complete fitting procedure of UV-Vis spectra of silver nanoparticles in colloidal solutions is reported. The fitting function, based on the Beer–Lambert law, Mie theory, and log-normal probability distribution of nanoparticles’ sizes, is developed and confirmed by 33 different independent measurements. In order to validate the accuracy of the function’s behavior on different spectra, freely accessible measurements were used, proving that the fitting function works independently of the method of their production—laser or chemical synthesis of nanoparticles. The developed fitting function is, to the best of our knowledge, novel and not based on any conventional spectral analysis approaches like the Mie–Gans procedure. Furthermore, since fitted parameters are all physical, it allows determination of the mode diameter of nanoparticles as well as the standard deviation of the log-normal distribution of sizes. It enables the reconstruction of size distribution of nanoparticles in colloidal solution. Step-by-step derivation of the fitting function is provided with a physical explanation of all parameters. The importance of Lorentzian dependence emerging at the core of Beer–Lambert law is physically discussed and linked to harmonic oscillator behavior of localized surface plasmon resonance of silver nanoparticles in a colloidal solution. Size distribution reconstruction from fitted parameters according to a log-normal distribution function is provided and a concentration calculation is presented. Full article
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18 pages, 6452 KiB  
Article
Simulation of the Nucleation and Crystal Growth Process in the Laser-Induced Deposition in Solution by a Lattice Boltzmann Method
by Yongsen He and Siyu Liu
Nanomaterials 2022, 12(18), 3213; https://doi.org/10.3390/nano12183213 - 16 Sep 2022
Cited by 1 | Viewed by 1662
Abstract
A Lattice Boltzmann model is proposed, combining the theories of nucleation and crystal growth for the study of the laser-induced deposition in solution (LIDS). The conjugate heat transfer and the natural convection of the liquid precursor were simulated with the evolving interface of [...] Read more.
A Lattice Boltzmann model is proposed, combining the theories of nucleation and crystal growth for the study of the laser-induced deposition in solution (LIDS). The conjugate heat transfer and the natural convection of the liquid precursor were simulated with the evolving interface of crystal growth. In turn, the morphology of the deposited materials was affected by multiple process parameters, including conditions of chemical precursor and the laser-induced heat and mass transfer. Simulation results indicated that the morphology of deposited materials was mostly affected by the initial concentration of the precursor solution. Specifically, the nonuniformity of thin films was caused by the convection induced by the pulsed-laser, and the surface roughness was due to the competition of local structures for the precursor supply. A relationship of process-condition-material was established, providing guidance of choosing various parameters in LIDS for a desirable morphology of deposited material, facilitating the capabilities of pulsed lasers in precise control in nanomanufacturing. Full article
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21 pages, 7752 KiB  
Article
Multiscale Kinetic Monte Carlo Simulation of Self-Organized Growth of GaN/AlN Quantum Dots
by Jorge A. Budagosky and Alberto García-Cristóbal
Nanomaterials 2022, 12(17), 3052; https://doi.org/10.3390/nano12173052 - 02 Sep 2022
Cited by 1 | Viewed by 1944
Abstract
A three-dimensional kinetic Monte Carlo methodology is developed to study the strained epitaxial growth of wurtzite GaN/AlN quantum dots. It describes the kinetics of effective GaN adatoms on an hexagonal lattice. The elastic strain energy is evaluated by a purposely devised procedure: first, [...] Read more.
A three-dimensional kinetic Monte Carlo methodology is developed to study the strained epitaxial growth of wurtzite GaN/AlN quantum dots. It describes the kinetics of effective GaN adatoms on an hexagonal lattice. The elastic strain energy is evaluated by a purposely devised procedure: first, we take advantage of the fact that the deformation in a lattice-mismatched heterostructure is equivalent to that obtained by assuming that one of the regions of the system is subjected to a properly chosen uniform stress (Eshelby inclusion concept), and then the strain is obtained by applying the Green’s function method. The standard Monte Carlo method has been modified to implement a multiscale algorithm that allows the isolated adatoms to perform long diffusion jumps. With these state-of-the art modifications, it is possible to perform efficiently simulations over large areas and long elapsed times. We have taylored the model to the conditions of molecular beam epitaxy under N-rich conditions. The corresponding simulations reproduce the different stages of the Stranski–Krastanov transition, showing quantitative agreement with the experimental findings concerning the critical deposition, and island size and density. The influence of growth parameters, such as the relative fluxes of Ga and N and the substrate temperature, is also studied and found to be consistent with the experimental observations. In addition, the growth of stacked layers of quantum dots is also simulated and the conditions for their vertical alignment and homogenization are illustrated. In summary, the developed methodology allows one to reproduce the main features of the self-organized quantum dot growth and to understand the microscopic mechanisms at play. Full article
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15 pages, 2352 KiB  
Article
Analytical Model of CVD Growth of Graphene on Cu(111) Surface
by Ilya Popov, Patrick Bügel, Mariana Kozlowska, Karin Fink, Felix Studt and Dmitry I. Sharapa
Nanomaterials 2022, 12(17), 2963; https://doi.org/10.3390/nano12172963 - 27 Aug 2022
Cited by 3 | Viewed by 2329
Abstract
Although the CVD synthesis of graphene on Cu(111) is an industrial process of outstanding importance, its theoretical description and modeling are hampered by its multiscale nature and the large number of elementary reactions involved. In this work, we propose an analytical model of [...] Read more.
Although the CVD synthesis of graphene on Cu(111) is an industrial process of outstanding importance, its theoretical description and modeling are hampered by its multiscale nature and the large number of elementary reactions involved. In this work, we propose an analytical model of graphene nucleation and growth on Cu(111) surfaces based on the combination of kinetic nucleation theory and the DFT simulations of elementary steps. In the framework of the proposed model, the mechanism of graphene nucleation is analyzed with particular emphasis on the roles played by the two main feeding species, C and C2. Our analysis reveals unexpected patterns of graphene growth, not typical for classical nucleation theories. In addition, we show that the proposed theory allows for the reproduction of the experimentally observed characteristics of polycrystalline graphene samples in the most computationally efficient way. Full article
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9 pages, 1495 KiB  
Article
Versatile Integrated Polarizers Based on Geometric Metasurfaces
by Zhiyuan Yue, Jilian Xu, Peiyao Lu and Shuyun Teng
Nanomaterials 2022, 12(16), 2816; https://doi.org/10.3390/nano12162816 - 17 Aug 2022
Cited by 1 | Viewed by 1592
Abstract
We propose versatile integrated polarizers based on geometric metasurfaces. Metasurface polarizer consists of an L-shaped hole array etched on a silver film, and it can simultaneously generate several polarization states, including linear polarization, circular polarization, elliptical polarization, or even hybrid polarization. Meanwhile, the [...] Read more.
We propose versatile integrated polarizers based on geometric metasurfaces. Metasurface polarizer consists of an L-shaped hole array etched on a silver film, and it can simultaneously generate several polarization states, including linear polarization, circular polarization, elliptical polarization, or even hybrid polarization. Meanwhile, the combination of output polarization states changes with the illumination polarization type. The theoretical analysis provides a detailed explanation for the generation of the integrated polarization states. The well-designed metasurface polarizers may generate more complex polarization modes, including vector beams and vector vortex beams. The theoretical and simulated results confirm the polarization performance of the proposed integrated metasurface polarizers. The compact design of metasurface polarizers and the controllable generation of versatile polarization combinations are a benefit to the applications of polarization light in optical imaging, biomedical sensing, and material processing. Full article
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12 pages, 1294 KiB  
Article
Modeling and X-ray Analysis of Defect Nanoclusters Formation in B4C under Ion Irradiation
by Matlab N. Mirzayev, Alexander A. Donkov, Evgeni A. Popov, Ertugrul Demir, Sakin H. Jabarov, Levan S. Chkhartishvili, Samuel A. Adeojo, Aleksandr S. Doroshkevich, Alexey A. Sidorin, Asif G. Asadov, Thabsile T. Thabethe, Mayeen U. Khandaker, Sultan Alamri, Hamid Osman, Alex V. Trukhanov and Sergei V. Trukhanov
Nanomaterials 2022, 12(15), 2644; https://doi.org/10.3390/nano12152644 - 31 Jul 2022
Cited by 9 | Viewed by 1544
Abstract
In the presented work, B4C was irradiated with xenon swift heavy ions at the energy of 167 MeV. The irradiation of the substrate was done at room temperature to a fluence of 3.83 × 1014 ion/cm2. The samples [...] Read more.
In the presented work, B4C was irradiated with xenon swift heavy ions at the energy of 167 MeV. The irradiation of the substrate was done at room temperature to a fluence of 3.83 × 1014 ion/cm2. The samples were then analyzed with the X-ray diffraction technique to study the structural modification, as it can probe the region of penetration of xenon atoms due to the low atomic number of the two elements involved in the material under study. The nano-cluster formation under ion irradiation was observed. Positron lifetime (PLT) calculations of the secondary point defects forming nanoclusters and introduced into the B4C substrate by hydrogen and helium implantation were also carried out with the Multigrid instead of the K-spAce (MIKA) simulation package. The X-ray diffraction results confirmed that the sample was B4C and it had a rhombohedral crystal structure. The X-ray diffraction indicated an increase in the lattice parameter due to the Swift heavy ion (SHI) irradiation. In B12-CCC, the difference between τ with the saturation of H or He in the defect is nearly 20 ps. Under the same conditions with B11C-CBC, there is approximately twice the value for the same deviation. Full article
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6 pages, 2064 KiB  
Article
DFT Analysis of Hole Qubits Spin State in Germanium Thin Layer
by Andrey Chibisov, Maxim Aleshin and Mary Chibisova
Nanomaterials 2022, 12(13), 2244; https://doi.org/10.3390/nano12132244 - 29 Jun 2022
Cited by 1 | Viewed by 1308
Abstract
Due to the presence of a strong spin–orbit interaction, hole qubits in germanium are increasingly being considered as candidates for quantum computing. These objects make it possible to create electrically controlled logic gates with the basic properties of scalability, a reasonable quantum error [...] Read more.
Due to the presence of a strong spin–orbit interaction, hole qubits in germanium are increasingly being considered as candidates for quantum computing. These objects make it possible to create electrically controlled logic gates with the basic properties of scalability, a reasonable quantum error correction, and the necessary speed of operation. In this paper, using the methods of quantum-mechanical calculations and considering the non-collinear magnetic interactions, the quantum states of the system 2D structure of Ge in the presence of even and odd numbers of holes were investigated. The spatial localizations of hole states were calculated, favorable quantum states were revealed, and the magnetic structural characteristics of the system were analyzed. Full article
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11 pages, 5390 KiB  
Article
Magnetic Force Probe Characterizations of Nanoscaled Ferromagnetic Domains: Finite-Element Magnetostatic Simulations
by Xiao-Xia Zheng and Wei-Feng Sun
Nanomaterials 2022, 12(13), 2212; https://doi.org/10.3390/nano12132212 - 28 Jun 2022
Cited by 2 | Viewed by 1441
Abstract
Microscopic characterization of magnetic nanomaterials by magnetic probe interacting with ferromagnetic nano-domains is proposed according to finite-element magnetostatic field simulations. Magnetic forces detected by microscopic probe are systematically investigated on magnetic moment orientation, magnetization intensity and geometry of ferromagnetic nano-domains, and especially on [...] Read more.
Microscopic characterization of magnetic nanomaterials by magnetic probe interacting with ferromagnetic nano-domains is proposed according to finite-element magnetostatic field simulations. Magnetic forces detected by microscopic probe are systematically investigated on magnetic moment orientation, magnetization intensity and geometry of ferromagnetic nano-domains, and especially on permanent magnetic coating thickness and tilting angle of probe, to provide a theoretical basis for developing magnetic force microscopy. Magnetic force direction is primarily determined by magnetic moment orientation of nanosample, and the tip curvature dominates magnetic force intensity that is meanwhile positively correlated with nanosample magnetization and probe magnetic coating thickness. Nanosample should reach a critical thickness determined by its transverse diameter to be capable of accurately detecting the magnetic properties of ferromagnetic nanomaterials. Magnetic force signal relies on probe inclination when the sample magnetic moment is along probe tilting direction, which, however, is not disturbed by probe inclination when sample magnetic moment is perpendicular to probe tilting plane. Within the geometry of satisfying a critical size requirement, the magnetic force can successfully image the ferromagnetic nano-domains by characterizing their sizes and magnetic moment orientations. The present study is expected to provide effective analyzing schemes and theoretical evidences for magnetic force microscopy of characterizing magnetic structures in ferromagnetic nanomaterials. Full article
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13 pages, 5207 KiB  
Article
Simulation and Modeling of Optical Properties of U, Th, Pb, and Co Nanoparticles of Interest to Nuclear Security Using Finite Element Analysis
by Elham Gharibshahi and Miltos Alamaniotis
Nanomaterials 2022, 12(10), 1710; https://doi.org/10.3390/nano12101710 - 17 May 2022
Cited by 1 | Viewed by 2308
Abstract
In this work, the optical characteristics of uranium (U), lead (Pb), cobalt (Co), and thorium (Th) nanoparticles are fashioned and simulated employing the finite element analysis (FEA) approach concerning multiple particle sizes. Applying finite element analysis, it was found that the simulated absorption [...] Read more.
In this work, the optical characteristics of uranium (U), lead (Pb), cobalt (Co), and thorium (Th) nanoparticles are fashioned and simulated employing the finite element analysis (FEA) approach concerning multiple particle sizes. Applying finite element analysis, it was found that the simulated absorption peaks of electronic excitations of nuclear nanoparticles are red-shifted from 365 nm to 555 nm for U; from 355 nm to 550 nm for Pb; from 415 nm to 610 nm for Co; and from 350 nm to 540 nm for Th, comparing expanding particle sizes from 60 nm to 100 nm (except for Co, which varied from 70 nm to 100 nm). The FEA-simulated optical band gap energies and far-field radiation patterns were also obtained for nuclear materials. The simulation approach in this research enables the prediction of optical properties and design of nuclear materials before manufacture for nuclear security applications. Full article
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11 pages, 4014 KiB  
Article
Computational Design of α-AsP/γ-AsP Vertical Two-Dimensional Homojunction for Photovoltaic Applications
by Yuliang Mao, Yuting Du, Zhipeng Huang, Guanhua Zhang and Jianmei Yuan
Nanomaterials 2022, 12(10), 1662; https://doi.org/10.3390/nano12101662 - 13 May 2022
Cited by 1 | Viewed by 1651
Abstract
Based on first-principles calculations, we design a α-AsP/γ-AsP homojunction with minimum lattice distortion. It is found that the α-AsP/γ-AsP homojunction has an indirect bandgap with an intrinsic type-II band alignment. The proposed α-AsP/γ-AsP homojunction exhibits high optical absorption of [...] Read more.
Based on first-principles calculations, we design a α-AsP/γ-AsP homojunction with minimum lattice distortion. It is found that the α-AsP/γ-AsP homojunction has an indirect bandgap with an intrinsic type-II band alignment. The proposed α-AsP/γ-AsP homojunction exhibits high optical absorption of 1.6×106 cm1 along the zigzag direction. A high power conversion efficiency (PCE) of 21.08% is achieved in the designed α-AsP/γ-AsP homojunction, which implies it has potential applications in solar cells. Under 4% in-plane axial strain along the zigzag direction, a transition from indirect band gap to direct band gap is found in the α-AsP/γ-AsP homojunction. Moreover, the intrinsic type-II band alignment can be tuned to type-I band alignment under in-plane strain, which is crucial for its potential application in optical devices. Full article
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